Abstract/Details

Chemistry in an inorganic -organic hybrid aerogel: Chitosan-silica aerogel


2005 2005

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Abstract (summary)

In this thesis, chemistry in a nanoporous inorganic-organic hybrid aerogel (X-silica aerogel) has been explored. The aerogel typically consisted of 10%w/w bioderived polymer (chitosan), and 90%w/w inorganic silica, which interact at the molecule level. The aerogel has a low density in the range of 0.2–0.3 g/cm3, high surface area in the range of 500–950m 2/g, and large pore volume about 90%. The pores are about 3–5 nm in diameter and the size of the primary particles comprising the aerogel network is about 1.5nm.

Chemical studies of X-silica aerogels were carried out in the first instance with organic molecules, including dansyl chloride (DC), succinic anhydride (SA), bis(4-isocynatocyclohexyl) methane (HMDI), and isocyanatoethyl methacrylate (IEMA). These reactions lead to modified X-silica aerogel products imparted with valuable functionalities, including fluorescence, carboxylic acid groups, and pendant isocyanate and methacrylate groups. The functionalized aerogels then were utilized to form novel composites. The isocyanate functionalized aerogels were combined with amine-containing silicone polymers to produce aerogel-silicone polymer composites, and methacrylate functionalized aerogels were reacted with hydroxyethylmethacrylate (HEMA) monomer to produce aerogel-polyHEMA composites.

The chemical studies were extended to gold-ion Au(III)-X-silica aerogels. Photoreduction of the Au(IIl)-X-silica aerogels by UV irradiation at 254nm reduced the Au(III) ions into Au(0) nanoparticles (AuNPs) while oxidizing the chitosan. Various sizes of AuNPs, with mean diameters from 8–87nm were obtained by varying the Au(III) ions concentration in aerogels from Au(III)/-NH 2 (-NH2 amine groups on chitosan) ratio 1:120 to 1:5. The intensity and time of exposure to the UV light were varied to explore their effect. Two dimensional patterns of Au(0)-X-silica aerogels were achieved by UV irradiation through a mask. Photo-reduction of Au(III)-X-silica aerogels in the presence of various thiols and disulfides leads to functionalized Au nanoparticles by the strong chemisorption of sulfurs and Au nanoparticles. Moreover, when these are present during the photolysis they control the growth of the gold nanoparticles.

Indexing (details)


Subject
Chemistry;
Materials science
Classification
0488: Chemistry
0794: Materials science
Identifier / keyword
Applied sciences; Pure sciences; Aerogel; Chitosan-silica; Inorganic-organic hybrid; Silica
Title
Chemistry in an inorganic -organic hybrid aerogel: Chitosan-silica aerogel
Author
Liu, Xipeng
Number of pages
212
Publication year
2005
Degree date
2005
School code
0024
Source
DAI-B 66/05, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9780542128004, 0542128004
Advisor
Risen, William M.
University/institution
Brown University
University location
United States -- Rhode Island
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3174640
ProQuest document ID
305029318
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/305029318
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